Controlling a oxygen liquefaction system responsive to a disturbance in supplied power

ABSTRACT

Normal operation of an oxygen liquefaction system ( 100 ) may be established responsive to a deviation in current supplied thereto. Current being supplied to a compressor ( 118 ) included in the oxygen liquefaction system may be monitored. The compressor may be deactivated responsive to commencement of a current level deviation event in the monitored current. The compressor may be energized responsive to cessation of the current level deviation event in the monitored current. Performance characteristics of the oxygen liquefaction system may be identified.

This patent application claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/317,438 filed on Mar. 25, 2010, the contents of which are herein incorporated by reference.

The invention relates to establishing normal operation of a liquefaction system responsive to a deviation in current supplied thereto.

Systems configured to liquefy fluids such as oxygen, nitrogen, and/or other fluids by reducing the temperature and increasing the pressure of the fluid being liquefied are known. Deviations in electrical power (e.g., surges, dips, and/or interrupts) supplied to such liquefaction systems can occur, for example, as a result of a fault in an associated power distribution system (e.g., open circuit breaker). A power distribution system fault can cause a switch in an associated distribution grid to open and close a number of times resulting in multiple interrupts to the oxygen liquefaction system. A large load being energized in the vicinity of a liquefaction system may also result in a deviation in electrical power supplied to the liquefaction system. While deviations in electrical supply may have a very short duration (e.g., a fraction of an AC-cycle, 20 AC-cycles, 40 AC-cycles, etc. (one AC-cycle at 60 Hz has a duration of 16.7 ms)), a refrigeration compressor of a liquefaction system may cease to operate properly or at all when subjected to such a deviation in electrical power supply.

Medical equipment, such as a liquefaction system for liquefying oxygen, may be required to demonstrate resistance or immunity to deviations in electrical power supply to insure continued reliable and safe operation when subjected such deviations. Conventionally, various circuit elements (e.g., fuses and/or breakers) associated with a refrigeration compressor of a liquefaction system may require resetting or replacement subsequent to a deviation in electrical power supply. Such resetting or replacement may require a user of a liquefaction system to possess some level of technical inclination, which cannot always be the case. Furthermore, the user of a conventional liquefaction system may need to be alerted that the system is not functioning properly.

Accordingly, it is an object of the present invention to provide an oxygen liquefaction system and method of using same that overcomes the shortcomings of conventional such systems. This object is achieved according to one embodiment of the present invention by providing a method for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto. The method includes monitoring the current being supplied to a compressor included in the oxygen liquefaction system. The method also includes deactivating the compressor responsive to commencement of a current level deviation event in the monitored current. The method further includes energizing the compressor responsive to cessation of the current level deviation event in the monitored current.

Another aspect of the invention relates to apparatus for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto. The apparatus includes a current monitoring device configured to monitor current being supplied to a refrigeration compressor included in the oxygen liquefaction system. The apparatus further includes a power modulation device configured to deactivate the refrigeration compressor responsive to commencement of a current level deviation event in the monitored current and to energize the refrigeration compressor responsive to cessation of the current level deviation event in the monitored current.

Yet another aspect of the invention relates to apparatus for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto. The apparatus includes a current monitoring means for monitoring current being supplied to a refrigeration compressor included in the oxygen liquefaction system. The apparatus also includes deactivation means for deactivating the refrigeration compressor responsive to commencement of a current level deviation event in the monitored current. The apparatus further includes energization means for energizing the refrigeration compressor responsive to cessation of the current level deviation event in the monitored current.

These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. In one embodiment of the invention, the structural components illustrated herein are drawn to scale. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not a limitation of the invention. In addition, it should be appreciated that structural features shown or described in any one embodiment herein can be used in other embodiments as well. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

FIG. 1 is a block diagram illustrating an exemplary oxygen liquefaction system configured to establish normal operation responsive to a deviation in current supplied thereto; and

FIG. 2 illustrates a method for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto, in accordance with one or more embodiments of the invention.

FIG. 1 is a block diagram illustrating an exemplary oxygen liquefaction system 100. The oxygen liquefaction system 100 is configured to establish normal operation responsive to a deviation in current supplied thereto. More specifically, by monitoring current supplied to a refrigeration compressor (described further herein) included in the oxygen liquefaction system 100, the refrigeration compressor can be deactivated responsive to commencement of a current level deviation event (e.g., surge, dip, and/or interrupt) in the monitored current, and can be energized responsive to cessation of the current level deviation event, in order to establish normal operation of the oxygen liquefaction system 100. As such, various components of the oxygen liquefaction system 100 do not require resetting or replacement after the oxygen liquefaction system 100 is subjected to a current level deviation event.

As depicted in FIG. 1, oxygen liquefaction system 100 includes a user interface 102, a liquefied oxygen generation unit 104, an oxygen generation unit 106, a refrigeration unit 108, a current monitoring device 110, and a power modulation unit 112. The description of the oxygen liquefaction system is illustrative and not intended to be limiting. For example, oxygen liquefaction system 100 may include additional components not necessary to describe the present technology. Additionally, while the present technology is described in the context of an oxygen liquefaction system, the concepts may be applied to any type of liquefaction system (e.g., a nitrogen liquefaction system).

User interface 102 is configured to provide an interface between the oxygen liquefaction system 100 and a user through which the user may provide information to and receive information from oxygen liquefaction system 100. This enables data, results, and/or instructions and any other communicable items, collectively referred to as “information,” to be communicated between the user and the oxygen liquefaction system. As used herein, the term “user” may refer to a single individual or a group of individuals who may be working in coordination. Examples of interface devices suitable for inclusion in user interface 102 include a keypad, buttons, switches, a keyboard, knobs, levers, a display screen, a touch screen, speakers, a microphone, an indicator light, an audible alarm, and a printer. In one embodiment, user interface 102 actually includes a plurality of separate interfaces.

It is to be understood that other communication techniques, either hard-wired or wireless, are also contemplated by the present invention as the user interface 102. For example, the present invention contemplates that the user interface may be integrated with a removable storage interface provided by an electronic storage (see, e.g., electronic storage 128 described further herein). In this example, information may be loaded into oxygen liquefaction system 100 from removable storage (e.g., a smart card, a flash drive, a removable disk, etc.) that enables the user(s) to customize the implementation of the oxygen liquefaction system. Other exemplary input devices and techniques adapted for use with the oxygen liquefaction system as user interface 102 include, but are not limited to, an RS-232 port, RF link, an IR link, modem (telephone, cable or other). In short, any technique for communicating information with oxygen liquefaction system 100 is contemplated by the present invention as the user interface 102.

Liquefied oxygen generation unit 104 may be configured to generate liquefied oxygen from gaseous oxygen. Liquefied oxygen may be generated from gaseous oxygen by reducing the temperature of the gaseous oxygen (e.g., to cryogenic levels) and/or by pressurizing the gaseous oxygen. The liquefied oxygen generation unit may include various components (not depicted) to generate and/or store liquefied oxygen, such as one or more of a heat exchanger, a dewar, and/or other components for generating and/or storing liquefied oxygen. The liquefied oxygen generation unit 104 is described further in connection with oxygen generation unit 106 and refrigeration unit 108.

Oxygen generation unit 106 may be configured to generate gas having high oxygen content (e.g., 93% pure medical grade oxygen) from gas provided via a gas intake 114. The gas provided via an gas intake 114 may include ambient air (approximately 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and small amounts of other gases), gas from a gas cylinder, and/or any other gas source. In exemplary embodiments, oxygen generation unit 106 generates gas having high oxygen content by way of a sieving process. Oxygen generation unit 106 may include various components (not depicted) to generate gas having high oxygen content, such as one or more of an air compressor, a fan, a sieve bed, and/or other components for generating gas having high oxygen content. In some embodiments, gas having high oxygen content may be pressurized by oxygen generation unit 106. Gas having high oxygen content may be delivered from the oxygen generation unit to the liquefied oxygen generation unit 104 via a purified oxygen line 116.

Refrigeration unit 108 may be configured to cool and circulate refrigerant utilized by liquefied oxygen generation unit 104 for generating liquefied oxygen. The refrigeration unit may include a refrigeration compressor 118 configured to drive circulation of the refrigerant, as well as various other components (not depicted) to cool or otherwise treat the refrigerant, such as one or more of a condenser coil, a fan, a hot separator, a cold separator, a filter, a dryer, and/or other components for cooling or otherwise treating the refrigerant. Cooled refrigerant may be delivered from the refrigeration unit 108 to the liquefied oxygen generation unit 104 via a cold refrigerant line 120, while spent refrigerant may be returned from the liquefied oxygen generation unit 104 to the refrigeration unit 108 via a hot refrigerant line 122.

According to some implementations, operation of refrigeration compressor 118 is binary in that the refrigeration compressor is either on (energized) or off (deactivated), whereas, in other embodiments, the refrigeration compressor may have one or more operating levels (e.g., a 60% operating level). Refrigeration compressor 118 may stop operating responsive to occurrence of a current level deviation event in the power delivered from power supply 124. Refrigeration compressor 118 may not resume normal operation when the current level deviation event ceases due to, for example, pressure differences between cold refrigerant line 120 and hot refrigerant line 122. That is, even though power may be supplied to the refrigeration compressor immediately after the refrigeration compressor has been deactivated during a current level deviation event, the refrigeration compressor may not properly drive circulation of the refrigerant.

Conventionally, confirmation of proper operation of a refrigeration compressor in an oxygen liquefaction system is obtained by monitoring production levels of liquefied oxygen. It can take 5 to 10 hours for a current level deviation event to reflect operation has returned to normal after the current level deviation event. Embodiments of the present technology, however, allow a current level deviation event to be detected. The refrigeration compressor may be deactivated such that the refrigeration compressor remains off even if the current level deviation event has ceased. The refrigeration compressor may be activated after the current level deviation event has ceased and after any pressure difference is reduced between cold refrigerant line 120 and hot refrigerant line 122. The current drawn by refrigeration compressor 118 being at a proper level may serve as confirmation that the refrigeration compressor is operating normally. Such a confirmation can be obtained substantially faster than conventional systems (e.g., about 30 minutes compared to 5 to 10 hours).

Refrigeration unit 108 and/or various components therein (e.g., refrigeration compressor 118) may receive electrical power from a power supply 124 via a power line 126. Current monitoring device 110 may be configured to monitor, measure, or otherwise probe current delivered via power line 126 from power supply 124 to the refrigeration unit 108 (or components therein). The current monitoring device may include any type of current sensing device such as a linear current sensor (e.g., Honeywell linear current sensor CSLA1CD), a current transformer, a Hall-effect sensor, and/or any other device suitable for determining the current delivered via power line 126.

Power modulation unit 112 may be communicatively coupled with current monitoring device 110, refrigeration unit 108, and/or other components of the oxygen liquefaction system 100. The power modulation unit may be configured to deactivate and/or energize refrigeration unit 108 and/or components therein (e.g., the refrigeration compressor) based at least in part on current delivered via power line 126, as determined by current monitoring device 110. In some embodiments, power modulation unit 112 may include circuitry (e.g., an RC circuit) configured to effectuate the functionalities attributed herein to the power modulation unit. In the embodiment illustrated by FIG. 1, power modulation unit 112 includes an electronic storage 128 and a processor 130.

In one embodiment, electronic storage 128 includes electronic storage media that electronically stores information. The electronic storage media of electronic storage 128 may include system storage that is provided integrally (i.e., substantially non-removable) with oxygen liquefaction system 100 and/or removable storage that is removably connectable to the oxygen liquefaction system via, for example, a port (e.g., a USB port, a firewire port, etc.) or a drive (e.g., a disk drive, etc.). Electronic storage 128 may include one or more of optically readable storage media (e.g., optical disks, etc.), magnetically readable storage media (e.g., magnetic tape, magnetic hard drive, floppy drive, etc.), electrical charge-based storage media (e.g., EEPROM, RAM, etc.), solid-state storage media (e.g., flash drive, etc.), and/or other electronically readable storage media. Electronic storage 128 may store software algorithms, information determined by processor 130, information received via user interface 102, and/or other information that enables oxygen liquefaction system 100 to function properly. The electronic storage may be a separate component within oxygen liquefaction system 100, or the electronic storage may be provided integrally with one or more other components of the oxygen liquefaction system (e.g., processor 130).

Processor 130 may be configured to provide information processing capabilities in oxygen liquefaction system 100. As such, the processor may include one or more of a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information. Although the processor is shown in FIG. 1 as a single entity, this is for illustrative purposes only. In some implementations, the processor may include a plurality of processing units. These processing units may be physically located within the same device or computing platform, or the processor may represent processing functionality of a plurality of devices operating in coordination.

As is shown in FIG. 1, processor 130 may be configured to execute one or more computer program modules. The one or more computer program modules may include one or more of an event detection module 132, a deactivation module 134, an activation module 136, a performance characteristic identification module 138, and/or other modules. The processor 130 may be configured to execute modules 132, 134, 136, and/or 138 by software; hardware; firmware; some combination of software, hardware, and/or firmware; and/or other mechanisms for configuring processing capabilities on the processor 130.

It should be appreciated that although modules 132, 134, 136, and 138 are illustrated in FIG. 1 as being co-located within a single processing unit, in implementations in which the processor 130 includes multiple processing units, one or more of modules 132, 134, 136, and/or 138 may be located remotely from the other modules. The description of the functionality provided by different modules 132, 134, 136, and/or 138 described below is for illustrative purposes, and is not intended to be limiting, as any of modules 132, 134, 136, and/or 138 may provide more or less functionality than is described. For example, one or more of modules 132, 134, 136, and/or 138 may be eliminated, and some or all of its functionality may be provided by other ones of modules 132, 134, 136, and/or 138. As another example, the processor 130 may be configured to execute one or more additional modules that may perform some or all of the functionality attributed below to one of modules 132, 134, 136, and/or 138.

Event detection module 132 may be configured to detect a current level deviation event. In exemplary embodiments, event detection module 132 may monitor the current level of power line 126, as determined by current monitoring device 110. The monitored current may breach a threshold level during such a current level deviation event. In some instances, the monitored current may exceed an upper threshold level, while in other instances, the monitored current may fall below a lower threshold level. Threshold levels may be predetermined, determined dynamically, inputted via the user interface 102, and/or be established in another way. The event detection module may identify commencement and/or cessation of a current level deviation event. According to some embodiments, event detection module 132 may provide an indication, such as via user interface 102, of a current level deviation event.

Deactivation module 134 may be configured to deactivate refrigeration compressor 118 responsive to commencement of a current level deviation event. In some embodiments, deactivation module 134 may effectuate actuation of a switch (not depicted) to electrically disconnect the refrigeration compressor from power supply 124. The deactivation module may deactivate the refrigeration compressor by deactivating a controller (not depicted) associated with the refrigeration compressor, in accordance with some embodiments.

Energization module 136 may be configured to energize refrigeration compressor 118 responsive to cessation of the current level deviation event. According to some embodiments, activation module 136 may effectuate actuation of a switch (not depicted) to electrically connect the refrigeration compressor to the power supply 124. Activation module 136 may activate refrigeration compressor 118 by activating a controller (not depicted) associated with the refrigeration compressor, in some embodiments. The activation module may delay activation of the refrigeration compressor for a period of time such that any pressure differential is reduced between cold refrigerant line 120 and hot refrigerant line 122.

Performance characteristic identification module 138 may be configured to identify one or more performance characteristics of oxygen liquefaction system 100. A performance characteristic may be identified based at least in part on the current level deviation event detected by event detection module 132 and/or the current being drawn by refrigeration compressor 118 from power supply 124 as measured by the current monitoring device 110. When refrigeration compressor 118 is drawing a proper level of current from power supply 124, the performance characteristic may be identified as normal operation. Responsive to the current monitored by the current monitoring device 110 falling below a threshold level, the performance characteristic may be identified as an open refrigeration compressor circuit. The performance characteristic may be identified as a potential refrigerant leak in response to the current monitored by current monitoring device 110 falls below a threshold level. The performance characteristic may be identified as a potential refrigerant blockage responsive to the current monitored by current monitoring device 110 exceeding the threshold level. According to some embodiments, an indication of a performance characteristic may be provided by performance characteristic identification module 138, such as via user interface 102.

FIG. 2 illustrates a method 200 for establishing normal operation of an oxygen liquefaction system (e.g., oxygen liquefaction system 100) responsive to a deviation in current supplied thereto, in accordance with one or more embodiments of the invention. The operations of method 200 presented below are intended to be illustrative. In some implementations, the method 200 may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of the method 200 are illustrated in FIG. 2 and described below is not intended to be limiting.

In some implementations, method 200 may be implemented in one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method 200 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of the method 200.

At an operation 202, current being supplied to a compressor (e.g., the refrigeration compressor 118) included in an oxygen liquefaction system (e.g., the current monitoring device 110) is monitored. In exemplary embodiments, the operation 202 may be performed by the current monitoring device 110 in conjunction with the power modulation unit 112 (or one or more modules thereof). For example, the event detection module 132 may detect a current level deviation event based on current measured by the current monitoring device 110.

At an operation 204, the compressor (e.g., refrigeration compressor 118) is deactivated responsive to commencement of a current level deviation event (e.g., surge, dip, and/or interrupt) in the monitored current (see operation 202). According to exemplary embodiments, operation 204 may be performed by the deactivation module 134. For example, the deactivation module 134 may effectuate actuation of a switch (not depicted in FIG. 1) to electrically disconnect the refrigeration compressor 118 from the power supply 124. As another example, the deactivation module 134 may deactivate the refrigeration compressor 118 by deactivating a controller (not depicted in FIG. 1) associated with the refrigeration compressor.

At an operation 206, the compressor (e.g., the refrigeration compressor 118) is energized responsive to cessation of the current level deviation event in the monitored current (see operation 202). The operation 206 may be performed by the activation module 136, in some embodiments. For example, activation module 136 may effectuate actuation of a switch (not depicted in FIG. 1) to electrically connect the refrigeration compressor 118 to power supply 124. As another example, the activation module 136 may activate refrigeration compressor 118 by activating a controller (not depicted in FIG. 1) associated with the refrigeration compressor. In accordance with exemplary embodiments, activation of the refrigeration compressor may be delayed for a period of time such any pressure differential is reduced between cold refrigerant line 120 and hot refrigerant line 122.

At an operation 208, one or more performance characteristics of the oxygen liquefaction system (e.g., oxygen liquefaction system 100) are identified based at least in part on the current level deviation event. Performance characteristic identification module 138 may perform operation 206, in accordance with exemplary embodiments. For example, when refrigeration compressor 118 is drawing a proper level of current from power supply 124, the performance characteristic may be identified as normal operation. As another example, responsive to the current monitored by current monitoring device 110 falling below a threshold level, the performance characteristic may be identified as an open refrigeration compressor circuit and/or a potential refrigerant leak. As yet another example, the performance characteristic may identified as a potential refrigerant blockage responsive to the current monitored by current monitoring device 110 exceeding the threshold level.

Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment. 

1. A method for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto, the method comprising: monitoring current being supplied to a compressor included in the oxygen liquefaction system; deactivating the compressor responsive to commencement of a current level deviation event in the monitored current; and energizing the compressor responsive to cessation of the current level deviation event in the monitored current.
 2. The method of claim 1, wherein the current level deviation event in the monitored current has a duration of less than 30 ms.
 3. The method of claim 1, further comprising identifying one or more performance characteristics of the oxygen liquefaction system.
 4. The method of claim 3, wherein an individual one of the one or more performance characteristics is identified as an open refrigeration compressor circuit or a potential refrigerant leak responsive to the monitored current falling below a threshold level.
 5. The method of claim 3, wherein an individual one of the one or more performance characteristics is identified as a potential refrigerant blockage responsive to the monitored current exceeding a threshold level.
 6. Apparatus for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto, the apparatus comprising: a current monitoring device configured to monitor current being supplied to a refrigeration compressor included in the oxygen liquefaction system; and a power modulation device configured to deactivate the refrigeration compressor responsive to commencement of a current level deviation event in the monitored current and to energize the refrigeration compressor responsive to cessation of the current level deviation event in the monitored current.
 7. The apparatus of claim 6, wherein the current level deviation event in the monitored current has a duration of less than 30 ms.
 8. The apparatus of claim 6, further comprising one or more processors configured to execute computer program modules, the computer program modules including a performance characteristic identification module configured to identify one or more performance characteristics of the oxygen liquefaction system.
 9. The apparatus of claim 8, wherein an individual one of the one or more performance characteristics is identified as an open refrigeration compressor circuit or a potential refrigerant leak responsive to the monitored current falling below a threshold level.
 10. The apparatus of claim 8, wherein an individual one of the one or more performance characteristics is identified as a potential refrigerant blockage responsive to the monitored current exceeding a threshold level.
 11. Apparatus for establishing normal operation of an oxygen liquefaction system responsive to a deviation in current supplied thereto, the apparatus comprising: current monitoring means for monitoring current being supplied to a refrigeration compressor included in the oxygen liquefaction system; deactivation means for deactivating the refrigeration compressor responsive to commencement of a current level deviation event in the monitored current; and energization means for energizing the refrigeration compressor responsive to cessation of the current level deviation event in the monitored current.
 12. The apparatus of claim 11, wherein the current level deviation event in the monitored current has a duration of less than 30 ms.
 13. The apparatus of claim 11, further comprising performance characteristic identification means for identifying one or more performance characteristics of the oxygen liquefaction system.
 14. The apparatus of claim 13, wherein an individual one of the one or more performance characteristics is identified as an open refrigeration compressor circuit or a potential refrigerant leak responsive to the monitored current falling below a threshold level.
 15. The apparatus of claim 13, wherein an individual one of the one or more performance characteristics is identified as a potential refrigerant blockage responsive to the monitored current exceeding a threshold level. 